string-substring-static-strings.js

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// `str.substring(...)` can return static strings.

const strings = [

  "abcdef",

  "ABCDEF",

];

for (let i = 0; i < 500; ++i) {

  let str = strings[i & 1];

  for (let j = 0; j < 2; ++j) {

    // One element static string.

    let r = str.substring(j, j + 1);

    assertEq(r, str.charAt(j));

    // Two elements static string.

    let s = str.substring(j, j + 2);

    assertEq(s, str.charAt(j) + str.charAt(j + 1));