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1 | 1 | # Coding Bootcamp JavaScript (JS)
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2 | 2 |
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3 | 3 | Our Coding bootcamp javascript 2020
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| 4 | + |
| 5 | +## Questions |
| 6 | + |
| 7 | +**Question:** How to find max and min number in an array using reduce method ? |
| 8 | + |
| 9 | +---------- |
| 10 | + |
| 11 | +**Question:**Try to fill in the blanks. (Without any changes) |
| 12 | +You can add some codes instead of ?????????. |
| 13 | +Answer: The output must be true. |
| 14 | + |
| 15 | +const x = ?????????; |
| 16 | +console.log(x == 5 && x == 25 && x == 125); // true |
| 17 | + |
| 18 | +Note: Please not search and google it. |
| 19 | +No time limit, anyone can think and try for this. |
| 20 | + |
| 21 | +---------- |
| 22 | + |
| 23 | +Concept: Consider the two functions below. Will they both return the same thing? Why and not? |
| 24 | +function t1() |
| 25 | +{ |
| 26 | + return { |
| 27 | + bar: "hello" |
| 28 | + }; |
| 29 | +} |
| 30 | +function t2() |
| 31 | +{ |
| 32 | + return |
| 33 | + { |
| 34 | + bar: "hello" |
| 35 | + }; |
| 36 | +} |
| 37 | +Test: |
| 38 | +console.log("t1:"); |
| 39 | +console.log(t1()); |
| 40 | +console.log("t2:"); |
| 41 | +console.log(t2()); |
| 42 | + |
| 43 | +---------- |
| 44 | + |
| 45 | +Are you familiar with data type and operators? |
| 46 | +If you think you are a js expert, think about this: |
| 47 | + |
| 48 | +**Question:**What will the code below output? Explain your answer. (guess the output) |
| 49 | +console.log(0.1 + 0.2); |
| 50 | +console.log(0.1 + 0.2 == 0.3); |
| 51 | + |
| 52 | +---------- |
| 53 | + |
| 54 | +**Question:**Write a add method which will work properly when invoked using either syntax below. |
| 55 | +console.log( add(2)(3) ); // Outputs: 5 |
| 56 | +console.log( add(4)(6) ); // Outputs: 10 |
| 57 | +console.log( add(6)(6) ); // Outputs: 12 |
| 58 | + |
| 59 | +------------ |
| 60 | + |
| 61 | +Okay, we go to next step: |
| 62 | + |
| 63 | +**Question:**Write a add method which will work properly when invoked using either syntax below. |
| 64 | +console.log( add(0) ); // Outputs: 0 |
| 65 | +console.log( add(2) ); // Outputs: 2 |
| 66 | +console.log( add(6) ); // Outputs: 6 |
| 67 | +console.log( add(2)(3) ); // Outputs: 5 |
| 68 | +console.log( add(4)(6) ); // Outputs: 10 |
| 69 | +console.log( add(6)(6) ); // Outputs: 12 |
| 70 | + |
| 71 | +------- |
| 72 | + |
| 73 | +But we have to expert in it to be sure of them. So trying... 👍 |
| 74 | + |
| 75 | +What about this? |
| 76 | +var cause a different in this case or no? |
| 77 | +const myNumber = '3'; |
| 78 | +(function (callback) { |
| 79 | + console.log(myNumber); |
| 80 | + var myText = 'hello'; |
| 81 | + callback(); |
| 82 | +})(function () { |
| 83 | + console.log(myNumber); |
| 84 | + console.log(myText); |
| 85 | + }) |
| 86 | + |
| 87 | +-------- |
| 88 | + |
| 89 | +So it will be interest at now: |
| 90 | +const myNumber = '3'; |
| 91 | +(function (callback) { |
| 92 | + console.log(myNumber); |
| 93 | + myText = 'hello'; |
| 94 | + callback(); |
| 95 | +})(function () { |
| 96 | + console.log(myNumber); |
| 97 | + console.log(myText); |
| 98 | + }) |
| 99 | + |
| 100 | +Guess it. |
| 101 | + |
| 102 | +---------- |
| 103 | + |
| 104 | +**Question:**What will the following code output and why? |
| 105 | +var b = 1; |
| 106 | +function outer(){ |
| 107 | + var b = 2 |
| 108 | + function inner(){ |
| 109 | + b++; |
| 110 | + let b = 5; |
| 111 | + console.log(b) |
| 112 | + } |
| 113 | + inner(); |
| 114 | +} |
| 115 | +outer(); |
| 116 | + |
| 117 | +------------ |
| 118 | + |
| 119 | +**Question:** What will the following code output and why? |
| 120 | +var b = 1; |
| 121 | +function outer(){ |
| 122 | + var b = 2 |
| 123 | + function inner(){ |
| 124 | + b++; |
| 125 | + var b = 5; |
| 126 | + console.log(b) |
| 127 | + } |
| 128 | + inner(); |
| 129 | +} |
| 130 | +outer(); |
| 131 | + |
| 132 | +---------- |
| 133 | + |
| 134 | +**Question:**Guess output |
| 135 | +console.log(color); |
| 136 | +const color = '#aaa'; |
| 137 | + |
| 138 | +---------- |
| 139 | + |
| 140 | +**Question:**Guess output |
| 141 | +console.log(color); |
| 142 | +var color = '#aaa'; |
| 143 | + |
| 144 | +---------- |
| 145 | + |
| 146 | +**Question:**Guess output |
| 147 | +console.log(color); |
| 148 | +let color = '#aaa'; |
| 149 | + |
| 150 | +---------- |
| 151 | + |
| 152 | +**Question:**Guess output |
| 153 | +function square(a = 4) { |
| 154 | + return a * a; |
| 155 | +} |
| 156 | +console.log( square() ); |
| 157 | + |
| 158 | +---------- |
| 159 | + |
| 160 | + |
| 161 | +**Question:**Guess output |
| 162 | +var a=4; |
| 163 | +function square(a = a) { |
| 164 | + return a * a; |
| 165 | +} |
| 166 | +console.log( square() ); |
| 167 | +console.log( square(2) ); |
| 168 | + |
| 169 | + |
| 170 | +---------- |
| 171 | + |
| 172 | + |
| 173 | +**Question:**Guess output |
| 174 | +let a=4; |
| 175 | +function square(a = a) { |
| 176 | + return a * a; |
| 177 | +} |
| 178 | +console.log( square() ); |
| 179 | +console.log( square(2) ); |
| 180 | + |
| 181 | +---------- |
| 182 | + |
| 183 | + |
| 184 | +**Question:**Guess output |
| 185 | +const a=4; |
| 186 | +function square(a = a) { |
| 187 | + return a * a; |
| 188 | +} |
| 189 | +console.log( square() ); |
| 190 | +console.log( square(2) ); |
| 191 | + |
| 192 | +---------- |
| 193 | + |
| 194 | +Question: |
| 195 | +function test(someVal) { |
| 196 | + typeof variable; // first question |
| 197 | + if (someVal) { |
| 198 | + typeof variable; // second question |
| 199 | + let variable; |
| 200 | + } |
| 201 | +} |
| 202 | +test(true); |
| 203 | + |
| 204 | +---------- |
| 205 | + |
| 206 | + |
| 207 | +**Question:**What will the code below output to the console and why? |
| 208 | + |
| 209 | +(function(){ |
| 210 | + var a = b = 3; |
| 211 | +})(); |
| 212 | +console.log("a defined? " + (typeof a !== 'undefined')); |
| 213 | +console.log("b defined? " + (typeof b !== 'undefined')); |
| 214 | + |
| 215 | +---------- |
| 216 | + |
| 217 | +**Question:**What will the code below output to the console and why? |
| 218 | + |
| 219 | +var myObject = { |
| 220 | + foo: "bar", |
| 221 | + func: function() { |
| 222 | + var self = this; |
| 223 | + console.log("outer func: this.foo = " + this.foo); |
| 224 | + console.log("outer func: self.foo = " + self.foo); |
| 225 | + (function() { |
| 226 | + console.log("inner func: this.foo = " + this.foo); |
| 227 | + console.log("inner func: self.foo = " + self.foo); |
| 228 | + }()); |
| 229 | + } |
| 230 | +}; |
| 231 | +myObject.func(); |
| 232 | + |
| 233 | +---------- |
| 234 | + |
| 235 | +**Question:**In what order will the numbers 1-4 be logged to the console when the code below is executed? Why? |
| 236 | +Guess order and why? |
| 237 | + |
| 238 | +(function() { |
| 239 | + console.log(1); |
| 240 | + setTimeout(function(){console.log(2)}, 1000); |
| 241 | + setTimeout(function(){console.log(3)}, 0); |
| 242 | + console.log(4); |
| 243 | +})(); |
| 244 | + |
| 245 | +---------- |
| 246 | + |
| 247 | +**Question:**Tell output of variables: |
| 248 | +var a = b = 3; |
| 249 | + |
| 250 | +---------- |
| 251 | + |
| 252 | +What's Palindrome? |
| 253 | +A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as madam, racecar. There are also numeric palindromes, including date/time stamps using short digits 11/11/11 11:11 and long digits 02/02/2020. |
| 254 | + |
| 255 | +**Question:**Write a simple function that returns a boolean indicating whether or not a string is a palindrome. |
| 256 | + |
| 257 | +Test case: |
| 258 | +— level => true |
| 259 | +— levels => false |
| 260 | + |
| 261 | +---------- |
| 262 | + |
| 263 | +**Question:**guess the d |
| 264 | +var d = {}; |
| 265 | +[ 'zebra', 'horse' ].forEach(function(k) { |
| 266 | + d[k] = undefined; |
| 267 | +}); |
| 268 | +console.log (d) |
| 269 | + |
| 270 | +---------- |
| 271 | + |
| 272 | +**Question:**What will the code below output to the console and why ? |
| 273 | + |
| 274 | +console.log(1 + "2" + "2"); |
| 275 | + |
| 276 | +---------- |
| 277 | + |
| 278 | + |
| 279 | +**Question:**What will the code below output to the console and why ? |
| 280 | + |
| 281 | +console.log(1 + +"2" + "2"); |
| 282 | + |
| 283 | +---------- |
| 284 | + |
| 285 | +**Question:**What will the code below output to the console and why ? |
| 286 | + |
| 287 | +console.log(1 + -"1" + "2"); |
| 288 | + |
| 289 | +---------- |
| 290 | + |
| 291 | +**Question:**What will the code below output to the console and why ? |
| 292 | + |
| 293 | +console.log(+"1" + "1" + "2"); |
| 294 | + |
| 295 | +---------- |
| 296 | + |
| 297 | +**Question:**What will the code below output to the console and why ? |
| 298 | + |
| 299 | +console.log( "A" - "B" + "2"); |
| 300 | + |
| 301 | +---------- |
| 302 | + |
| 303 | +**Question:**What will the code below output to the console and why ? |
| 304 | + |
| 305 | +console.log( "A" - "B" + 2); |
| 306 | + |
| 307 | +---------- |
| 308 | + |
| 309 | + |
| 310 | +**Question:**What will be the output of the following code: |
| 311 | + |
| 312 | +for (var i = 0; i < 5; i++) { |
| 313 | + setTimeout(function() { console.log(i); }, i * 1000 ); |
| 314 | +} |
| 315 | + |
| 316 | +---------- |
| 317 | + |
| 318 | + |
| 319 | +**Question:**What is the output out of the following code? Explain your answer. |
| 320 | +var a={}, |
| 321 | + b={key:'b'}, |
| 322 | + c={key:'c'}; |
| 323 | +a[b]=123; |
| 324 | +a[c]=456; |
| 325 | +console.log(a[b]); |
| 326 | + |
| 327 | +---------- |
| 328 | + |
| 329 | +**Question:**guess output |
| 330 | +console.log( + "***" ); |
| 331 | + |
| 332 | +---------- |
| 333 | + |
| 334 | +**Question:**guess output |
| 335 | +console.log(- "***" ); |
| 336 | + |
| 337 | +---------- |
| 338 | + |
| 339 | +**Question:**guess output |
| 340 | +console.log( new Number(5) == 5); |
| 341 | +console.log( new Number(5) == 5 == "5"); |
| 342 | +console.log( new Number(5) == 5 == "5" == new Number(6)); |
| 343 | + |
| 344 | +---------- |
| 345 | + |
| 346 | +**Question:**guess output |
| 347 | +console.log( new Number(5) === 5); |
| 348 | + |
| 349 | +---------- |
| 350 | + |
| 351 | +**Question:**guess output |
| 352 | +class test { |
| 353 | + #age=45; |
| 354 | +} |
| 355 | +g=new test(); |
| 356 | +g.age |
| 357 | + |
| 358 | +---------- |
| 359 | + |
| 360 | +**Question:**guess output |
| 361 | +#age=45; |
| 362 | + |
| 363 | +---------- |
| 364 | + |
| 365 | +**Question:**JavaScript is an OOP scripting language? or no? |
| 366 | + |
| 367 | +---------- |
| 368 | + |
| 369 | +**Question:**guess output |
| 370 | +p=new Point(); |
| 371 | +console.log(p);// first answer |
| 372 | + |
| 373 | +p=new Point(4);// second answer |
| 374 | +console.log(p);// third answer |
| 375 | +console.log(p.toString()); //forth answer |
| 376 | + |
| 377 | +---------- |
| 378 | + |
| 379 | +**Question:**guess output |
| 380 | +0.1 + "0.2" |
| 381 | +"0.1" + 0.2 |
| 382 | + |
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